Making Craters...
That Won't Crater Your Wallet!

Materials:
Thick brown felt
White glue (AKA "Elmer's Glue")
Sand
Dark Brown Spray Paint
Light Brown Acrylic Paint and a Cheapo Paint Brush
As always, I get all of my materials at my local hardware store or discount retailer (AKA Wal-Mart). Don't buy any of these materials "name brand" there is no point in it.
The size of craters will depend on what scale of figures you use. But, in the case of craters you will most likely want to make them in several different sizes anyway. But, even with 28mm figures your largest craters is likely to be no more than 5-6" across and the smallest should be able to fit a single stand/base/figure... So, if you can find felt in the "pieces bin" at a local fabric store you may be able to pick up all you need for a lifetime for a couple of bucks. Try to get felt of a decent thickness as it will help make your craters tougher.
As with all my terrain you will need a quantity of white glue but any white glue will do so get the cheapest brand you can find.
You will need a fair quantity of sand. I get "Play Sand" at Wal-Mart and it generally costs between $1.50 and $2.50 for a 20lb bag. This is substantially cheaper than the 6-8 oz "hobby sand" sold at game/craft stores (you do the math). Once painted you won't be able to tell the difference and actually the differing sizes of sand grains found in the cheap play sand is better for what we want.
You will need a can or two of flat dark brown paint. And some light brown acrylic paint and a brush. Use a cheap brush as it will most likely be shot to hell after this project and you won't need anything nice to do what we have planned... <g>
Construction:
The first thing you need to do is to decide how big to make your craters. Again, I would suggest that the minimum size for any crater to be is the size of a single figure base/stand. With that in mind then add in another 1/4" to 1/2" around the edges. Cut your felts into irregular circle-shapes in the sizes you want. Do them in several different sizes keeping in mind that different soil types/conditions as well as different weapons and angles of impact all make different sized craters.
After you have all your little felt pieces cut out. Dip them in a wash/mix of white glue and water. I would suggest the mix be at least 50-75% glue (the more the better). Then lay them flat and let them dry. Be sure they are laid flat because when they dry the felt will be very stiff. Also you should lay them on something they will not stick to. I would suggest wax paper or something of that sort. I am lucky enough to have a hunk of granite I use (don't ask).
After they are dry and nice and stiff, take and smear white glue (no mix here, pure glue) around the edges for about 1/8"-1/2". With the glue still wet sprinkle sand on them. Sprinkle as much sand as you can on them and let this dry. Again, make sure they are flat as they dry. Repeat the "sand sprinkle process" several times until you get the edges of the craters built up to where you like them. How thick you want them built up is very dependant on what scale of figures you use and your personal taste. I did mine over a course of several days in between painting batches. Handle them gently at this stage as the sand will tend to flake off. We will deal with that in the next step...
Then after the craters are completely dry set them outside in a large group and spray the holy heck out of them with the dark brown spray paint. After they are dry (drying time can vary widely, felt is almost as bad as sponges!) do it again or several more times for strength if you like. The spray paint acts as a very good glue-hardening agent if you use it in enough quantity. Wal-Mart spray paint is cheap and strong. Cheap and strong is good so don't be shy on using a lot of it. <g>
Then, hit them with a dry brush from your light brown acrylic paint using a cheapo brush (because the sand is holy hell on brushes). Let them dry, and you are done!
With basically a nights worth of effort I made all the craters I will ever need for about $7.00
They look darn good, they are dirt cheap and can be produced in a hurry. Yep, that's my mantra when it comes to terrain building! <G>
These are a pair of trenches and are made the exact same way as the craters above. Just, cut your felt accordingly!
All content copyright R. Scott Clinton